Several of this year's major wildfires have burned in unforested areas.

"Every year, as the fire's (sic) rage & California burns, it is the same thing - and then he comes to the Federal Government for $$$ help. No more. Get your act together Governor," Mr Trump wrote on Twitter.

Mr Newsom, who has been highly critical of Mr Trump's environmental policies, responded: "You don't believe in climate change. You are excused from this conversation."

Increased temperatures due to global warming are causing huge wildfires in California regardless of how wet the previous winter was, according to a recent study published in the Proceedings of the National Academy of Sciences.

Drier, warmer conditions lead to vegetation drying out and becoming more flammable.

The president made a similar threat to cut federal aid last year, when the most deadly fire in California's history killed 86 people.

What's happening with the fires?

Firefighters have contained about half of the Maria Fire, the major blaze in southern California.

The fire, which broke out on Thursday, has burned more than 9,400 acres, the Ventura County Fire Department said on Sunday.

The largest blaze, the Kincade Fire in Sonoma County, was 76% contained on Sunday after burning nearly 80,000 acres since it started on 23 October, officials said.